1. Field of the Invention
This invention relates generally to medical instruments for retrieving and withdrawing clots from the vasculature, and more particularly concerns a shape memory clot retrieval device having an elongated catheter member with at least one clot retrieval member connected to the elongated catheter member that is movable between an initial compressed configuration in which the clot retrieval device is inserted into the vasculature and an expanded configuration extending outwardly from the elongated catheter member to trap and hold clots within the vessel.
2. Description of Related Art
Recently developed interventional procedures have been used to treat defects in the vasculature which are not easily reached by surgical procedures. More particularly, such interventional procedures have been developed to treat defects that are located in small and remote vessels such as those within the brain. During such interventional procedures, vasoocclusive devices are typically placed within the vasculature of the human body by use of a catheter, either to block the flow of blood through a vessel making up that portion of the vasculature through the formation of an embolus, or to form such an embolus within an aneurysm stemming from the vessel. When an embolus generating vasoocclusive device is used to treat an aneurysm, the success of the treatment generally depends upon whether the embolus generating vasoocclusive device can migrate out of the aneurysm through the neck of the aneurysm. Migration of the embolus generated out of the aneurysm into the parent vessel poses a danger to the patient, so that it would be desirable to provide a device for retrieving and withdrawing such an embolus, whether the embolus has been created by an embolus generating vasoocclusive device or otherwise.
One conventional technique for retrieving deleterious materials such as an embolus from body lumens involves the use of a retrieval catheter having a slack net at its distal end that is operated by a pull wire, that may be collapsed to facilitate introduction of the catheter into a body lumen, and that may be opened when necessary to permit capture and retrieval of the deleterious materials. The slack net structure is secured to a flexible loop member which is secured to the pull wire, and the flexible loop member is formed from resilient materials possessing a memory so that when pull wire is retracted, the loop member will regain a preset circular configuration. However, such a structure is relatively bulky and cumbersome, making the technique difficult to employ in more distal areas of the vasculature with narrow lumens, such as in the brain.
A catheter apparatus is also known that employs a shape memory alloy structure as an actuator for a thin shutter door to open and close a radially disposed opening in the catheter for collecting plaque. While this apparatus is suitable for collecting plaque on the inside of a blood vessel, it is not generally effective for retrieving and withdrawing an embolus that may be loose or free floating within the vasculature. Another known technique uses an adjustable closed wire loop or snare that is manipulated over an object to be retrieved, and in one such apparatus, the surgical snare is made from a shape memory material that can be trained to remember a specific configuration. However, these types of surgical snares can require great care and dexterity for their operation in acquiring an embolus, and an embolus can easily escape, so that it would be desirable to provide a system for retrieving and withdrawing an embolus within the vasculature of a patient that can be deployed in narrow, distal vessels for trapping and holding distal loose or free floating clots. The present invention meets these needs.
Briefly, and in general terms, the present invention provides for an improved shape memory clot retrieval device that can be placed in the vasculature of a patient for retrieving and removing distal clots. The clot retrieval device advantageously has an elongated catheter member that can be inserted in the vasculature, with one or more clot retrieval members on the elongated catheter member that are movable between an initial compressed configuration in which the clot retrieval device is inserted into the vasculature and an expanded configuration extending outwardly from the elongated catheter member to trap and hold clots within the vessel. The clot retrieval device typically can be introduced to the desired treatment site in the vasculature through a delivery catheter.
The invention accordingly provides for an apparatus for removing clots from the vasculature of a patient, comprising an elongated catheter member, and one or more clot retrieval members connected to the elongated catheter member. The one or more clot retrieval members are advantageously formed from a shape memory material so that they are movable upon activation between an initial compressed configuration and an expanded configuration extending outwardly from the elongated catheter member to trap and hold clots within the vessel. The elongated catheter member is adapted to be placed within a vessel of the patient when the one or more clot retrieval members are in the compressed configuration, and is adapted to be removed from the vessel when the clot retrieval members are in the expanded configuration, whereby clots trapped by the clot retrieval members can be withdrawn from the vessel. In a presently preferred aspect, the clot retrieval members are formed from a shape memory material, preferably having a glass transition temperature (Tg) above body temperature, and having a desired compressed configuration at a temperature appropriate for introduction into the body via a catheter, and an expanded configuration with the one or more clot retrieval members extending outwardly that is assumed upon activation.
The shape memory material is currently preferably a shape memory polymer, such as polyurethane, heat shrink tubing such as polyethylene, polyethylene terephthalate (PET) or high density polyethylene (HDPE), although the shape memory material may alternatively be a shape memory metal such as nickel titanium alloy, such as that available under the trade name NITINOL, for example, that can be heat treated to have shape memory behavior. As the clot retrieval members are activated by heat, the activated shape memory clot retrieval members open radially and outwardly to catch and hold clots in the vasculature.
A heat activation member is also preferably provided for heating the one or more clot retrieval members to cause them to expand radially outwardly from the elongated catheter member. In a presently preferred aspect, the heat activation member typically can be advanced axially through the middle of the elongated catheter member and the one or more clot retrieval members to be positioned adjacent to the one or more clot retrieval members. The heat activation member currently preferably comprises an optical fiber, although the heat activation member can also comprise a heat pipe, or a device for generating heat by RF energy, or the like.
In one presently preferred embodiment, the elongated catheter member is tubular, and the one or more clot retrieval members comprise a tubular member formed from a shape memory material having a tubular wall defining a plurality of ridges and valleys. The ridges and valleys are movable between an initial compressed configuration in which the ridges and valleys are substantially flattened, to an expanded configuration wherein the ridges extend outwardly from the valleys of the elongated catheter member to trap and hold clots within the vessel. The elongated catheter member is thus adapted to be placed within a vessel of the patient when the plurality of ridges and valleys are in the compressed, flattened configuration and removed from the vessel when the ridges and valleys are in the expanded configuration, whereby clots trapped by the ridges and valleys can be withdrawn from the vessel. In a presently preferred aspect, the ridges and valleys of the clot retrieval tubular member are initially compressed axially, radially, or both.
In another presently preferred embodiment, the one or more clot retrieval members comprise a plurality of tab members connected to the elongated catheter member. The plurality of tab members are movable between an initial compressed configuration to an expanded configuration extending outwardly from the elongated catheter member to trap and hold clots within the vessel, and the elongated catheter member is adapted to be placed within a vessel of the patient when the tab members are in the compressed configuration and removed from the vessel when the tab members are in the expanded configuration, whereby clots trapped by the tab members can be withdrawn from the vessel.
In one presently preferred embodiment, the elongated catheter member comprises an elongated, tubular member, and the one or more clot retrieval members are formed from the tubular wall of the elongated tubular member, defining a plurality of tab members that are initially compressed axially, radially, or both to extend contiguously with the surface of the tubular wall. In a preferred aspect, the elongated tubular member and tab members are formed from a shape memory material.
In an alternate preferred embodiment, the elongated catheter member carries one or more clot retrieval members that can comprise an annular ring, preferably formed from a shape memory material, connected to the elongated catheter member, with the annular ring having an initial compressed configuration in which the annular ring is compressed radially against the surface of the elongated catheter member, and an expanded configuration in which the annular ring projects outwardly from the surface of the elongated catheter member, whereby the extended annular ring can trap and hold a blood clot.
In another presently preferred alternate embodiment, the elongated catheter member carries a plurality of tab members, with each of the tab members being connected at one end to the elongated catheter member and having a free end, with the tab members having an initial compressed configuration in which the tab members are compressed against the surface of the elongated catheter member and an expanded configuration in which the tab members project outward radially from the surface of the elongated catheter member, whereby the extended tab members can trap and hold a blood clot. The tab members can be initially compressed axially, radially, or both. In a presently preferred aspect, the tab members are formed from a shape memory material.
In yet another presently preferred embodiment, the apparatus for removing clots comprises an elongated catheter member and the clot retrieval member comprises an elongated sheet or ribbon of shape memory material having first and second ends connected to the elongated catheter member, with the elongated sheet of shape memory material wound in a helical configuration about the elongated catheter member. The ribbon of shape memory material has an initial compressed configuration in which the ribbon of shape memory material is compressed radially against the surface of the elongated catheter member and an expanded configuration in which the ribbon of shape memory material projects outward radially from the surface of the elongated catheter member, whereby the extended ribbon of shape memory material can trap and hold a blood clot.
These and other aspects and advantages of the invention will become apparent from the following detailed description and the accompanying drawings, which illustrate by way of example the features of the invention.